Direct current motors have been suggested heretofore which employ, inter alia, a commutator and associated brushes. In such arrangements, the brushes require substantially continuous maintenance and, after a period of use, wear out and require replacement. In addition, such motors cannot be practically operated at higher voltages due to the sparking which results at the commutator.
In an effort to avoid some of these difficulties, motors have been suggested heretofore which use solid state elements as commutation devices. Arrangements of this general type are described, for example, in the U.S. Pat. Nos. to Thompson 3,200,315, Hetzel 3,229,179, Kuniyoshi et al. 3,522,499, Thornton et al. 3,619,746, Kuniyoshi 3,749,991, Greenwell 3,753,060 and 3,753,062, Carow 3,766,456, and Bourbeau 3,866,099. While these prior arrangements eliminate some of the known difficulties of brush-type motors, they nevertheless are so constructed that they must operate at low power levels. In contrast, the motor of the present invention has no practical upper power limit and is adapted for use, for example, at voltages in excess of 10,000 volts.
The system of the present invention is adapted for use with motors of various conventional shapes and with magnetic stator structures of various conventional configurations. However the system has been found to exhibit particular advantages when employed in conjunction with an axial airgap motor structure of the type described in my prior U.S. Pat. No. 3,567,978 wherein at least one stator is associated with at least two rotors arranged in an axial airgap type of construction. Such a construction has the advantage of lower weight and higher efficiency, but due to its provision of several rotors would, when operated on direct current as contemplated by the present invention rather than on alternating current as described in said patent, require several commutators or a large number of interconnections between the rotors. The novel construction of the present invention permits the use of axial airgap motors with several rotors without encountering such complications.
Inasmuch as the magnetic structure of the motor used in a preferred embodiment of the present invention is described in my above-identified prior patent, the disclosure of said prior patent is incorporated herein by reference.
The present invention finds particular advantages when employed as the motor power source of an electric motor vehicle due to the fact that substantially all possible trouble caused by wear, dirt, and handling by nontechnical persons, are eliminated.